Liam Hockley

Higher Degree by Research Candidate

School of Physics, Chemistry and Earth Sciences

Faculty of Sciences, Engineering and Technology


I am a final year PhD student at the University of Adelaide. My area of research is in theoretical particle physics, specifically the investigation of baryon resonances and their structure. Lattice QCD is the established first principles approach for such studies, but the connection between lattice calculations on a finite volume and experimentally observed resonances in infinite volume is highly non-trivial. While Luscher's method is typically used for making these connections, it becomes cumbersome to work with when including multiple scattering channels and possibly a mixture of 2- and 3-body decays. For my work, I've incorporated an approximately equivalent method known as Hamiltonian Effective Field Theory, which centres on a Hamiltonian that is built from a phenomenological perspective and constrained using experimental data. While HEFT allows for the same interpretations of LQCD data as Luscher's method, it offers additional insight into the nature of resonances through the Hamiltonian eigenvectors, which encode information like 3-quark content. These methods are of particular interest for studying the light baryon resonances and the Roper puzzle, which has held tension with the quark model of baryons for decades.

Current Research Projects:

I am currently in my first year of my PhD, with the prospective thesis title Baryonic Resonances in Hamiltonian Effective Field Theory and Lattice QCD.

In a nutshell, my research is aimed at better understanding the structure of excited states of low-lying baryons such as the nucleon and the Delta. Historically the nucleon case has been particularly challenging since the parity of its first excited state contradicts the expected parity from a harmonic oscillator model for a state composed of 3 quarks. Recent work by the University of Adelaide suggests that rather than taking this first excited state (known as the Roper resonance) to be a naive 3-quark state, one should instead adopt the model of a state generated dynamically through various scattering channels. I'm hoping to verify this interpretation by studying the similarly troublesome excited states of the Delta baryon.

The initial aim of this work is to compare the mass spectrum of the Delta resonances obtained through both Lattice QCD and Hamiltonian Effective Field Theory (HEFT) in order to comment on the Delta(1600) as being a dynamically generated resonance. To realise this, we will construct an effective Hamiltonian involving several relevant scattering channels for the Delta(1600), namely: pion-nucleon, pion-Delta(1232) and sigma-Delta(1232). We will then look to solve the Hamiltonian for its eigenstates and thus produce an energy spectrum for the Delta resonance. If it is found that this spectrum is comparable to that generated via Lattice QCD, this would corraborate similar findings for the historically troublesome Roper resonance.

 

Previous Research Projects:

Other than my current work in hadronic physics on the lattice, I also have an interest in the role CP violation plays in understanding the matter-antimatter imbalance in the universe. My Masters thesis title was Direct CP Violation in B Meson Decays, and I specifically focused on the CP violation effects in B->K+ K- pi decays. In order to calculate direct CP violation in these decays, I calculated the CP asymmetry arising from the interference between relevant tree and penguin diagrams. I employed well known tools such as Effective Hamiltonians and Naive Factorisation Approximations to do this. The first of these methods allows one to describe the amplitudes of particle decays in terms of products of quark currents in the Operator Product Expansion, while the second provides the means for simplifying the resultant matrix elements. One then calculates these matrix elements using form factors for which we took well known models.

  • Education

    Date Institution name Country Title
    2020 - 2024 The University of Adelaide Australia (In progress) Doctor of Philosophy (Physics)
    2018 - 2020 The University of Adelaide Australia Master of Philosophy (Physics)
    2015 - 2017 The University of Adelaide Australia Bachelor of Science (Advanced)
  • Research Interests

  • Journals

    Year Citation
    2024 Hockley, L., Kamleh, W., Leinweber, D., & Thomas, A. (2024). Searching for the first radial excitation of the Δ(1232) in lattice QCD. Journal of Physics G: Nuclear and Particle Physics, 51(6), 24 pages.
    DOI
    2023 Hockley, L., Kamleh, W., Leinweber, D., & Thomas, A. (2023). Δ Baryon Spectroscopy in Lattice QCD. Few-Body Systems, 64(3), 1-10.
    DOI
  • Preprint

    Year Citation
    2024 Hockley, L., Abell, C., Leinweber, D., & Thomas, A. (2024). Understanding the nature of the $Δ(1600)$ resonance.
    2024 Leinweber, D. B., Abell, C. D., Hockley, L. C., Kamleh, W., Liu, Z. -W., Stokes, F. M., . . . Wu, J. -J. (2024). Understanding the nature of baryon resonances.
    2023 Hockley, L., Kamleh, W., Leinweber, D., & Thomas, A. (2023). Searching for the first radial excitation of the $Δ(1232)$ in
    lattice QCD.

Barker Tong Scholarship (2020-)

Research Training Stipend (2020-)

Master of Philosophy (no Honours) Scholarship (2018-2020)

Current Teaching Positions:

Quantum Mechanics III Workshop Mentor (2020 semester 2)

 

Previous Teaching Positions:

Physics III - Quantum Mechanics Workshop Mentor (2020, semester 1) - Topics: Schrodinger equation in 1D and 3D, harmonic oscillator, angular momentum, hydrogen atom.

Physics IB Workshop Mentor (2019, semester 2) - Topics: Rotational Mechanics, Special Relativity and Quantum Mechanics. 

Physics IA Workshop Mentor (2019, semester 1) - Topics: Mechanics, Electromagnetism.


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